Anil SononeTech Blog

Friday, August 23, 2024

Worker Node – In Kubernetes Overview

A worker node provides a running environment for client applications
In Kubernetes the application containers are encapsulated in Pods, controlled by the cluster control plane agents
Pod is the smallest scheduling work unit in Kubernetes.
in a multi-worker Kubernetes cluster, the network traffic is handled directly by the worker nodes, and is not routed through the control plane node.

Kubernetes supports several container runtimes:
CRI-O : A lightweight container runtime for Kubernetes,
Containerd : A simple and portable container runtime.
Docker Engine : A popular and complex container platform which uses containerd as a container runtime.
Mirantis Container Runtime : Formerly known as the Docker Enterprise Edition.

2. Node Agent - kubelet

The kubelet is an agent running on each control plane node and workers node
It receives Pod definitions, from the API Server, and interacts with the container to run containers in the Pod.
The kubelet connects to container runtimes through a plugin interface like imageService and runtimeService
The ImageService is responsible for all the image-related operations, while the
RuntimeService is responsible for all the Pod and container-related operations.

3. Proxy - kube-proxy

Kube-proxy is Network agent which runs on each control plane node and workers node
implements forwarding rules through Service API objects.
The kube-proxy node agent operates with the iptables of the node.
Iptables is a firewall utility created for the Linux OS

4. Add-ons

are cluster features not yet available in Kubernetes, therefore implemented through 3rd-party services.

is a DNS server required to assign DNS records to Kubernetes objects and resources.

Collects cluster-level container logs and saves them to a central log store for analysis.